Merge bitcoin/bitcoin#25986: test: refactor RPCPackagesTest to use MiniWallet

17cad44 test: refactor `RPCPackagesTest` to use `MiniWallet` (w0xlt)

Pull request description:

  This PR refactors `RPCPackagesTest` to use `MiniWallet` and removes `create_child_with_parents`, `make_chain`, and `create_raw_chain` from `test_framework/wallet`, as requested in bitcoin/bitcoin#25965.

  Close bitcoin/bitcoin#25965.

ACKs for top commit:
  glozow:
    ACK 17cad44
  pablomartin4btc:
    tested ACK 17cad44; went thru all changes and recommendations from @kouloumos & @glozow; also went up to #20833 to get a bit of background of the origin and purpose of these tests.
  kouloumos:
    ACK 17cad44

Tree-SHA512: 9228c532afaecedd577019dbc56f8749046d66f904dd69eb23e7ca3d7806e2132d90af29be276c7635fefb37ef348ae781eb3b225cd6741b20300e6f381041c3

Author: glozow